1. Field of the Invention
The present invention relates to a charge control apparatus for a battery pack having a cooling structure, and more specifically relates to a charge control apparatus for a battery pack using the ambient temperature of the battery.
2. Description of the Related Art
Japanese Laid-open Publication No. 8-148187 discloses a technique of controlling the temperature of a battery through a heat-transfer plate by controlling the external temperature.
In the charge control of a battery pack having an air cooling structure, the temporal change dT/dt of the battery temperature is controlled based on a battery temperature TB and the air temperature TA, which is represented by the following formula:
dT/dt=(TBxe2x88x92TB-1)+K(TBxe2x88x92TA), 
where:
TB is the battery temperature;
TA is the air temperature; and
K is the heat radiation coefficient.
In the charge control of a battery pack having a liquid cooling structure, the temporal change dT/dt of the battery temperature is controlled based on the battery temperature TB and a coolant temperature TW, which is represented by the following formula:
dT/dt=(TBxe2x88x92TB-1)+K(TBxe2x88x92TW), 
where:
TB is the battery temperature;
TW is the coolant temperature; and
K is the heat radiation coefficient.
In a battery pack having a cooling structure, however, the battery temperature is affected not only by the coolant temperature but also by the ambient temperature. Therefore, if the temporal change dT/dt of the battery temperature is controlled based only on the battery temperature and the coolant temperature, a precise control of the temporal change dT/dt of the battery temperature Is impossible in the case where the difference between the ambient temperature and the coolant temperature is great.
Also, in the case where the difference between the ambient temperature and the battery temperature is great, the battery temperature is affected by the ambient temperature. As a result, the baseline of the temporal change dT/dt of the battery temperature varies as the ambient temperature varies. Accordingly, the charge capacity of the battery fluctuates greatly in accordance with the ambient temperature.
The charge control apparatus for a battery pack having a cooling structure of this invention includes: a coolant temperature sensor for detecting temperature of a refrigerant which cools the battery pack; a battery temperature sensor for detecting a battery temperature of the battery pack; an ambient temperature sensor for detecting an ambient temperature of the battery pack; and a control section for controlling the charge of the battery pack, based on the refrigerant temperature detected by the refrigerant temperature sensor, the battery temperature detected by the battery temperature sensor and the ambient temperature detected by the ambient temperature sensor.
In another aspect of the invention, a charge control apparatus for an EV battery having a liquid cooling structure includes: a coolant temperature sensor for detecting a coolant temperature of coolant which refrigerates the EV battery; a battery temperature sensor for detecting a battery temperature of the EV battery; an ambient temperature sensor for detecting an ambient temperature of the EV battery; and a control section for controlling the charge of the EV battery, based on the coolant temperature detected by the coolant temperature sensor, the battery temperature detected by the battery temperature sensor and the ambient temperature detected by the ambient temperature sensor.
In one embodiment of the invention, the control section may control the charge capacity of the battery pack based on a value of a temporal change dT/dt of the battery temperature of the battery pack, when:
dT/dt=(TBxe2x88x92TB-1)+(KW/1+k)xc3x97(TBxe2x88x92(TW+kTA)/(1+k))+((kxc3x97kA)/(1+k))xc3x97(TBxe2x88x92((TW+kxc3x97TA)/(1+k)), 
where:
dT/dt is the temporal change of the battery temperature;
TW is the refrigerant temperature;
TA is the ambient temperature;
TB is the battery temperature;
KW is the heat radiation coefficient of the refrigerant;
kA is the heat radiation coefficient of the ambient; and
k is the coefficient defining the final resultant temperature of the battery.
In another embodiment of the present invention, the control section may control the charge capacity of the EV battery based on a value of a temporal change dT/dt of the battery temperature of the EV battery, when:
dT/dt=(TB=TB-1)+(KW/1+k)xc3x97(TBxe2x88x92(TW+kTA)/(1+k))+((kxc3x97kA)/(1+k))xc3x97(TBxe2x88x92((TW÷kxc3x97TA)/(1+k)), 
where:
dT/dt is the temporal change of the battery temperature;
TW the coolant temperature;
TA is the ambient temperature;
TB is the battery temperature:
KW is the heat radiation coefficient of the coolant;
kA is the heat radiation coefficient of the environment; and
k is the coefficient defining the final resultant temperature of the battery.
In another embodiment of the invention a charge control apparatus for a battery pack may further include a circulator for supplying the refrigerant to the battery pack.
In still another embodiment of the invention a charge control apparatus for an EV battery according to claim 2 may further include a circulator for supplying the coolant to the EV battery
Thus, the invention described herein makes possible the advantages of (1) providing a charge control apparatus for a battery pack, which Is capable of precisely controlling the temporal change dT/dt of the battery temperature even when the difference between the ambient temperature and the coolant temperature is great, and (2) providing a charge control apparatus for a battery pack, in which the fluctuation of the charge capacity of the battery caused by the difference of the ambient temperature is small.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.